1. Field of the Invention
Embodiments of the present invention generally relate to devices used by pilots to determine entry into a holding pattern.
2. Description of the Related Art
Both commercial and general aviation flying depend on weather and flight rules defined by Federal Aviation Administration (FAA). If the weather is good and the flight is below 18,000 feet the FAA may permit aircraft to fly using simple visual flight rules (VFR). Under VFR a pilot may only operate at minimum prescribed distances from clouds and defined visibility. If the visibility is restricted or the airplane must fly in the clouds or if the flight is above 18,000 feet, more rigorous instrument flight rules (IFR) must be followed. Under IFR the pilot flies by reference to the aircraft instruments and follows special, IFR navigational charts. Most IFR flights must be coordinated by aircraft traffic control (ATC). Under most conditions, the pilot must be in two-way radio communication with ATC. As in the case of ground traffic, there can be heavy traffic in the air, particularly near airports.
While ground traffic can and often does come to full stop, aircraft, other than helicopters or balloons, cannot stop. Therefore, in lieu of coming to a complete stop in the air, ATC may instruct the pilot to fly a prescribed oval or race track shaped shape pattern called hold. The hold is generally defined in location and orientation by reference to a local navigational transmitter. The FAA also prescribes the entry method in which the pilot enters the hold. The entry method depends on a direction the airplane approaches the hold and the orientation of the hold. There are three standard entry methods. These are direct entry, parallel entry, and teardrop entry. Once established in the hold, the pilot will make all turns to the right, unless otherwise instructed by ATC or indicated by IFR navigational charts. When all the turns are made to the right, the holding pattern is called a right holding pattern or standard hold. When all turns are made to the left, the holding pattern is called a left holding pattern or nonstandard hold. In order to determine the correct entry method into the hold, the pilot must calculate an angle between the orientation of the hold and the heading of the airplane. The pilot must then take into account whether the holding pattern is a right or left holding pattern. Unfortunately, the entry method for entering the hold can be difficult to compute and visualize especially under stress associated with operating an aircraft in an IFR environment. Often the pilot makes a mistake and uses the wrong entry method, sometimes with serious consequences.
There are, several devices available to help with the calculation of the entry method. Unfortunately, these devices are designed for use in the classroom and in training and are lacking in simplicity, speed, and complete information. Moreover, such devices are additional equipment to find in an already tight cockpit and are not easily attached to a pilot's knee-board. Moreover, such devices typically require two hands to operate and do not automatically provide an indication with north at the top, thus inducing the typical pilot to make a sketch of the holding pattern and entry method. Therefore, what is needed is an apparatus that will enable a pilot under the stress of instrument conditions to quickly determine and visualize a holding pattern orientation and the entry method for entering the holding pattern, that can be attached to a knee-board and can easily operated with one hand, while in flight.